1. Field of the Invention
The present invention relates to an address allocation method using IP site-local prefix pools in mobile ad-hoc networks (MANETs), and more particularly, to a method of allocating duplication-free site-local prefixes to allocate addresses to nodes so that the allocated addresses can adapt to merging or partitioning of the MANETs.
2. Description of the Related Art
With the development of mobile communication devices and technologies, the necessity of small-sized wireless communication networks, in addition to the existing infrastructure network, is increased. In particular, more attention is focused on the small-scale wireless networks under environments which are liable to be isolated from the external Internet and where wired equipment is impractical such as in emergency situations, airplanes, inside of buildings, mountain regions, and so on. A mobile ad-hoc network (MANET) can be an example for such a small-scale wireless communication network.
Different from the infrastructure network, the MANET does not have an independent router receiving and forwarding packets, but has each mobile node serve as both a host and a router. Further, a node on the MANET can roam since it has a wireless communication device, so that the topology of the MANET is not fixed.
Since each node on the MANET has a limited transmission range on its wireless signals, packets may not be directly forwarded from a source node to a destination node. For such a case, packets are forwarded via a plurality of nodes serving as routers, which is referred to as a “multi-hop” mechanism, and the MANET needs a routing protocol to implement the multi-hop mechanism.
A uniqueness-guaranteed IP address has to be allocated to each node to route packets in the MANET. To do so, research is progressing to support the network environment for diverse mobile hosts to connect to the Internet in the MANET using the IPv6 address autoconfiguration, which is an Internet address scheme.
Different from past efforts in which research has focused on packet routing, research is actively progressing on network configuration and management in the MANET research field in recent. However, such research mainly relates to a scheme allocating duplication-free IP addresses, in consideration of network configuration and management, to mobile nodes attempting to take part in one MANET, and the Internet Engineering Task Force (IETF) MANET working group is centered on the active lines of research, but less attention is paid to research on an environment in which plural MANETs merge in a group.
A node attempting to participate in the MANET has to be allocated an address to be used in a corresponding MANET. To do this, the node generates a temporary address in a method such as address autoconfiguration, and performs Duplicate Address Detection (DAD) to confirm whether the generated address is a unique address in the corresponding MANET.
FIG. 1 is a flow chart showing a DAD process in a conventional mobile ad-hoc network. Referring to FIG. 1, if a network is formed with plural mobile nodes participating in operation S110, then each of the participated mobile nodes generates its own Link-Layer Address (LLA) in operation S115, and sends a Neighbor Solicitation (NS) message including the generated LLA to the entire network in operation S120 to start the DAD.
The mobile node decides whether to receive a Neighbor Advertisement (NA) message notifying of address duplication within a predetermined limited time RetransTimer in operation S125. If the mobile node fails to receive the NA message until the NS message has been resent as many times as the predetermined number of times in operation S130, the corresponding LLA is recognized as a unique address so that the LLA of the mobile node is confirmed in operation S135, and the mobile node performs communications using the LLA.
In the meantime, the topology of a MANET can vary all the time since nodes participating in the MANET have mobility as a characteristic, so the MANET can exist as one independent MANET, two or more independent MANETs can merge, or one independent MANET can be partitioned into two or more MANETs. However, the merging and partitioning of two or more mobile MANETs are not taken into consideration in the conventional method. Therefore, a method is needed which allocates uniqueness-guaranteed IP addresses in an environment taking the merging and partitioning into account.
The IP addresses are classed into a Link-local address, a site-local address, and global address based on a scope a corresponding address is applied to. The Link-local address is an address scoped to a corresponding link for communications with a neighboring node connected to the same link, and the site-local address is scoped to a corresponding local site. The global address has no limit to its scope.
Currently, one prefix is globally applied to all MANETs for a site-local prefix used upon generating an IPv6 site-local address for communications with outside networks in the MANET, or the site-local prefix is randomly selected for each MANET.
When the site-local prefix is globally used for all MANETs, the prefix is restricted in use. Further, it is impossible to allocate addresses in MANETs-clustered environments.
When each MANET randomly selects a site-local prefix, an additional DAD process among the networks is required to verify the uniqueness of the selected prefix since one network can not know the site-local prefix of the other network, which causes a waste of network resources. With the development of mobile communication devices and technologies, the necessity of small-sized wireless communication networks, in addition to the existing infrastructure network, is increasing. In particular, more attention is focused on the small-scale wireless networks under environments liable to isolate from external internet and wired equipment is impractical such as in emergency situations, airplanes, inside of buildings, mountain regions, and so on. A mobile ad-hoc network (MANET) is an example of such a small-scale wireless communication network.